Biodiesel process : RHT-Biodiesel

ABSTRACT

This invention covers a process for making biodiesel from vegetable oils and animal fat with a simple hetrogeneous catalyst providing high yield and reaction rates under moderate conditions. The process is designed so as to enhance the yield by pretreatment step of esterification if required. The process provides gravity separation and any pretreatment/distillation/stripping, if needed before sending Biodiesel and glycerine to storage. The process provides heterogeneous catalysts so as to reduce the waste from the system and also it reduces the utilities and chemical cost. The process is optimized, simple in operation, economical, providing best yields compared to any processes in the market.

FIELD OF THE INVENTION

The invention relates to producing biodiesel from palm oil, Rape seed, vegetable and animal product that are all fatty acids with even number of carbon atom typically 12 to 22 atoms. It does not produce sulfur dioxide, less carcinogen fumes and less black smoke. The lack of sulfur in the biodiesel means it meets all international specification once the boiling range is right, and these are comparable to hydrocarbon diesel. The triglyceride feeds make biodieseel, reacting these triglycerides with methanol/ethanol or higher alcohols which all produce biodiesel in the acceptable boiling range. Methanol is most commonly used for the biodiesel production as being the cheapest alcohol, hence provides better economics. Biodiesel is produced by vegetable oils and animal fats (triglycerides) into fatty acid methyl esters. The process requires a pretreatment step to remove the free fatty acids so as to enhance the yield of esters. The first step is esterification of the free fatty acid, (if these are more than 3 wt % in the feed) with methanol. These triglycerides are than converted by transesterification reaction with methanol to form methyl esters of those oils. Fats, and glycerine is produced as a byproduct. Glycerine is separated from the methyl esters that is biodiesel, by phase separation by gravity settling due to density differences.

BACKGROUND OF THE INVENTION

With the hydrocarbon fuels prices going up and the renewable fuel mandate and the environmental advantages of the biodiesel as mentioned above it is expected that there will be activity in this area so as to supplement the hydrocarbon fuels, which will help in reducing demand of Crude oil.

The process is based on esterification of free fatty acid, a pretreatment step so as to enhance the yield of methyl esters in transesterification reaction. The esterification reaction is done with free fatty acids in Feed with methanol in the presence of a cation acid ion exchange resin catalyst Lewatit K 2621, K 2620 or equivalent (Rohm Haas Amberlyst 15 or 35 or Dowex M 31). This removes most of Free Fatty acids and increases the yield of Biodiesel. The reaction conditions are in 100 to 200 F. temperature and pressure of 20 to 150 psig (preferably 50 psig and temperature 140 F.) to perform this reaction in the Esterification reactor.

The second reaction to is transesterification of triglycerides from oil or fats with methanol in the presence of alkaline catalyst. The catalysts that are being used are in homogeneous form, predominantly KOH. New processes have started using hetrogeneous catalyst that improves the process in removing major liquid wastes from this process, which are due to homogeneous catalyst use. RHT-Biodiesel process is based on hetrogeneous catalyst like Potassium carbonate, Barium sulfate, Calcium aluminate, Cobalt carbonate, Polyamine, Ammonical metal-oxide, Sodium, Potassium and Calcium Phosphates, mixture of metal oxides with alumina, Magnesium methoxide, Calcium oxide, Calcium ethoxide and baron hydroxide, Calcinated hydro zeolite, and any other alkaline heterogeneous compounds available in market including the Anion ion exchange basic catalyst which can also be used like Amberlyst A-21, Amberlyst A26 or equivalent but not limited to. The operating conditions for transesterification are similar to esterification reaction.

The transesterification reactor effluent provides essentially 100 percent conversion to Methyl Esters of the Fatty acid/triglycerides feeds. This is sent to gravity separator where glycerine settles at the bottom, as its specific gravity is 1.2 to 1.3. The methyl esters and normal specific gravity is in the range of 0.85 to 0.9.

The biodiesel is taken from top of the separator and is washed with water before sending it to the storage. The glycerine is taken from the bottom of the gravity separator and is also washed with water before sending it to storage. Water wash will contain methanol that can be recovered by distillation and recycled to the process.

SUMMARY OF THE INVENTION

The process in this art claims that vegetable oils and animal fats can be converted to Biodiesel that has properties very close to the petroleum based diesel and actually produces fewer emissions that petroleum based diesel. The biodiesel refers to esters made from the vegetable or animal fats. At present biodiesel is being mixed with petroleum based diesel in some markets, but it can be used on its own in the current diesel engines. With the flash point of 220 to 320 F, OSHA has classified biodiesel as non-flammable liquid.

The process in this art claims that the vegetable oils and animal fat can be converted to biodiesel by reacting these with methanol or ethanol and other alcohol to make an ester by suing heterogeneous catalyst which are alkaline solids compounds are with basic resin catalysts. The process first converts the free fatty acid and these reduce the reaction rate and phase separation after the reaction. First Vegetable oils are esterified reacting with methanol in the presence of acid resin catalyst at moderate temperatures and than transesterified in the second reactor to Oil Methyl Ester (biodiesel) by transesterification reaction, which is triglycerides reacting with methanol to form biodiesel in the presence of basic Catalyst at moderate temperatures and pressure. The art here claims that by using hetrogeneous catalyst reduces the water or netrulization/soap produced in the conventional process. Glycerine is produced as a by-product of this process. an alternate solution to glycerin removal from the reactor is also suggested, together with the hetrogeneous catalyst application which reduces the waste treatment problem.

The reactor effluent is separated in a simple gravity settler and sent to storage after water wash. The final product can be vacuum stripped if so desired but there are not many requirements for it in this process.

The art is in the esterification and transesterification reaction catalyst selection that enhances the yield and reduces the liquid effluents from the process described. Additionally it provides some advantages of additional transesterification reactor use in the process so as to get the maximum reaction rates and on stream factor.

The art of the process provides the spare reactor to be washed with hot solvent so as to remove the residual glycerol from the catalyst that reduces the reaction rates. This solvent is taken off site for stripping of the solvent from glycerine. The solvent is recycled where as recovered glycerine can be sent to the glycerine product.

The reactions are also done at moderate temperatures that are less energy intensive than conventional process.

This unique feature will be apparent to one who is skilled in the art from the figures and claims and brief description of the FIGS. 1 and 2.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a simplified process flow diagram of the process, where the feed of vegetable oil or animal fats is pumped from storage to the operating pressure of 50 to 80 psig stream 1, The feed with methanol in the molar ratio of 6 to 8 vegetable/methanol. The feed is heated to the reaction temperature 120 to 200 F. (preferably 160 F.) and is fed to (stream 4) esterification reactor item 2 so as to convert all the free fatty acid, if these are present more than 3 percent in the feed. The WHSV in this reactor is kept 2 to 10 (preferably at about 3 to 4). The reactor contains Acid cation resin catalyst Lewatit K 2621, K2620 or equivalent (Rohm Haas Amberlyst 15 or 35 or Dowex M 31). This removes 99.9% of Free Fatty acids and the reactor (item 2) effluent is fed to the transesterification reactor item 5. Where 3 moles of methanol react with the triglyceride to produce 3 moles of oil methyl ester (biodiesel) and one mole of glycerine. The pressure and temperatures are essentially the same as esterification reactor. The transesterification reactor item5, has hetrogeneous catalyst from following compounds, Potassium carbonate, Barium sulfate, Calcium aluminize, Cobalt carbonate, any other alkaline hetrogeneous compounds available in market including the Anion ion exchange basic catalyst which can also be used like Amberlyst A-21, Amberlyst A26 or equivalent but not limited to. The WHSV for the catalyst is in the range of 2 to 10 but preferably 2 to 3 will provide essentially 100% conversion. The transesterification reactor effluent stream 6 is sent to gravity separator item 7. The biodieseel product is taken from the top of the separator as stream 8. This should be good to send to the storage but if need be it can be washed with water as shown in the water wash drum. The Biodieseel product is taken as Stream 9. Water wash will provide excess methanol to be extracted and recovered by normal distillation of pure methanol that is recycled back to the reactor. The bottom from the separator item 7 Stream 11 is taken and is good to be sent as glycerine product to storage. But to have better quality glycerine, it should be washed in the similar mode as biodieseel, so as to remove methanol from glycerine stream. Glycerine is taken as stream 12 and sent to storage and methanol/water mixture is sent to same distillation column to purify the methanol that is recycled to the front of the process. These reduce the methanol make up requirements.

FIG. 2 is alternate mode of the simple process flow diagram of the above flow scheme and all things are same except a spare transesterification reactor Item 5 is provided so as to remove the glycerine from the reactor which reduces the reaction rates. Once the reaction rates are reduced the reactor is switched and washed with hot solvent so as to remove residual glycerine and biodiesel. This extra reactor provides higher reactions rates and on stream factor enhancing the yield and productivity of the process.

DETAILED DESCRIPTION OF THE INVENTION

The major art and know how described here is a disclosure of producing Biodiesel from vegetable oil/animal fats, first removing the Free fatty acids by esterification with methanol in the presence of with hetrogeneous catalyst in the fixed bed reactor so as to improve the yield and reaction rates. The effluent from this reactor is transesterified with methanol with hetrogeneous catalyst in the fixed bed reactor. The products are separated in gravity separator and are washed and sent to storage. As mentioned earlier optimum operating conditions and WHSV is provided so as to get the reaction to essentially 100% completion.

The alternate option is provided so as to enhance the reaction rates and also on stream factor for transesterification reactor item 5.

Based on the configuration and feed compositions following conditions will be required for the Esterification (if Free Fatty acids are more than 3% in the Feed) and Transesterification Fixed bed reactors, and could be down flow or upflow configuration:

Inlet Temp (F.) 100 to 200 (120 to 160 F. preferable) Pressure (psig) 50-to 80 LHSV (hr)⁻¹ 2 to 10 (preferably 3 to 5) Free fatty acids (FFA) and tryglycerides Conversion 99.9%

Reaction Chemistry

Vegetable Oil/Animal Fat Transesterification Reactions:

Comparison of the Diesel/Biodieseel Properties

Fuel Property Diesel Biodiesel Fuel Standard ASTM D 975 ASTM P S 121 Fuel Composition C10-C21 HC C12-C22 FAME Lower Heating Value 131 117 Btu/gal Kinemetic Vis @ 40 C. 1.3-4.1 1.9-6.0 SG at 60 F. 0.85 0.88 Water wppm 161 500 Carbon 87 77 Hydrogen 13 12 Oxygen 0 11 Sulfur wppm  15-500 0 Bp F 380-650 370-340 Flash Pt F 140-175 210-140 

1. Process for producing Biodiesel comprising the following: (a) Free fatty acid in the feed are converted to triglycerides by reacting the feed with methanol, Esterification reaction, in the presence of acid ion exchange resin catalyst in the first fixed bed reactor; (b) Resin catalyst can be Lewatit K2621, K2620, Rohm Haas Amberlyst 15/35 or Dowex M31 or equivalent; (c) The WHSV of 2 to 5 is provided in the first fixed bed reactor; (d) Reactor operating conditions of 120 to 160 F. temperatures and 50 to 80-psig pressure and can be operated in up flow or down flow mode; (e) The methanol is provided in the molar ratio of vegetable oil (fat)/methanol of 6 to 9; (f) (canceled) (g) The invention provides the highest yield to ester by first removing the Free Fatty Acids if these are over 3 wt % in the Feed; (h) The process of claim 1 is a major improvement that enhances the yield and economics for Bio-diesel process by converting free fatty acids to triglycerides. cm
 2. The second claim being: (a) triglycerides are converted to biodiesel (Ester of oil/Fats) by reacting with methanol (alcohol) by transesterification reaction in the presence of alkaline catalyst, which are defined in claim 2 (e) below; (b) Transesterification reactor operating conditions of 120 to 160 F temperature and 50 to 80 psig pressure are used, in the second fixed bed reactor with heterogeneous catalyst; (c) WHSV of 2 to 5 is provided for transesterification reaction in the second fixed bed reactor and could operate in up flow or down flow mode; (d) The methanol is provided in the molar ratio of vegetable oil (fat)/methanol of 6 to 9; (e) The heterogenous catalyst for transesterification reaction is alkaline like, Sodium, Potassium and Calcium Phosphates, Magnesium methoxide, Calcium oxide, Calcium ethoxide and boron hydroxide, Calcinated hydrozeolite or any other higher alkaline hetrogeneous compound available including the basic ion exchange catalyst like Amberlyst A-21, Amberlyst A-26 or equivalent but not limited to; (f) (canceled) (g) The Ester/Biodiesel and Glycerine produced in the transesterification reaction are separated in gravity separator by phase separation; (h) Both the products are further distilled to meet the product specification; (i) To enhance the on stream factor spare transesterification reactor is provided in the configuration to enhance the process technology economics as the glycerol produced in the reaction, reduces the reaction rates with time; (j) (canceled) (k) The process of claim 2 and a spare reactor and heterogeneous catalyst are the major claims, which enhances the economics and no liquid waste is produced as is produced in the classical KOH lye catalyst process.
 3. The third claim being: (a) The procedure to clean the reactor which is taken off from the operation after the reaction rates are reduced due to catalyst being covered with glycerine: The catalyst in the reactor taken off the operation, is washed with hot alkaline solvent/solution to remove the glycerol from catalyst and get the activity back; (b) In the configuration provision is there for a special means to remove the impurities from both product (biodiesel) and byproduct (Glycerol) by water wash in the drums; (c) The process provides possibility of using adsorption/absorption to remove the certain impurities in Biodiesel product or Glycerol byproduct, if so desired; (d) Additional provision is to remove any impurities in product and byproduct by classical Vacuum distillation/or stripping methods or under positive pressure, which ever is most economical. 